Cell Reselection for a mobile radio communications device User equipment (UE) operating within a cellular network comprises an important capability offering many advantages to both the user, and the network operator, and having regard in particular to load-management and continuity of service.
It can therefore been seen as important to achieve efficient, reliable and accurate cell reselection as and when candidate neighbouring cells are available.
Current reselection procedures involve measurement techniques that employ a measurement quantity but which exhibit disadvantages which serve to limit, and possibly prevent, reselection to the most appropriate neighbouring cell.
A requirement for accurate and efficient reselection procedures becomes particularly acute when a candidate neighbouring cell for reselection comprises a Femtocell.
As will be appreciated, Femtocells are defined by low-power, small local base stations, and generally employed to provide local radio coverage within, for example, a residential environment, a dead zone such as where no macro cell coverage is available, WiFi-type hot spots and also small-to-medium enterprise environments.
For example, insofar as 3G Macro Cells operate on high frequencies in the range of 2 GHz-3 GHz, it is appreciated that they offer poor coverage/signal strength within buildings. Poor wall penetration, and the higher absorption characteristics, at such higher frequencies limit performance in this manner. Such poor “in-building” performance leads to small area within marco cell coverage where limited, or indeed no-coverage, is available.
The provision of Femtocells can therefore prove advantageous in effectively filling-in the gaps that such in-building environments can define within the macro cell environment.
A further advantage that arises from employing Femtocells is that they can assist the overall performance within the macro cell environment by effectively reducing the load on the macro cell infrastructure. Thus the use of Femtocells provides a mechanism for dealing with poor coverage issues, whilst also offering potential benefits such as increased capacity on the macro cell, and for the ready commercial provision of bundled services, such as: DSL Broadband and Mobile Phone services.
Femtocells also appear attractive to an end user in so far as much more cost effective mobile voice and data calls can be made, while also experiencing improved domestic coverage.
Reselection to a Femtocell for example in poor coverage environments is therefore an attractive proposition, and so such cells will then compete with other neighbouring cells, both Femto or Macro, during such reselection procedures.
With regard to deployment, it will be appreciated that such Femtocells can be operated with various different operational characteristics, for example, whether on the same, or different, carrier frequency as the neighbouring macro cell(s).